Since the 80s a new branch of medicine based on the use of short-range static electric fields to stimulate positive biological processes in the human body has formed and rapidly developed. The main distinguishing feature of practical methods that are based on this concept is that electric fields are not made by traditional electrical power sources with network or battery power, it is made by autonomously functioning electret films.
Electret is a dielectric on the surface or in the bulk of which non-compensated electric charges are preserved for a long time. These charges produce an electric field in the space surrounding an electret. Getting together with an implant to the human body, an electret film by its field has a local effect on the damaged organ, contributing to its treatment. The electric field of certain magnitude and sign, acting at the cellular level, is the catalyst of reparative processes in living tissues.
US 2005/0059972 A1 discloses a pedical screw including a head and a lower portion wherein to the head is connected a head-piece, wherein different head-pieces can be connected to the pedical screw. The lower portion of the pedical screw includes a thread for anchoring the pedical screw in a bone.
Similarly, US 2009/0048675 A1 represents a general prior art for the present invention, disclosing a bone fusion device, comprising a body portion, a first inserting portion extending from the body portion for engaging a first bone, and a second inserting portion extending from the body portion for engaging a second bone.
A method for treatment arthrosis of the femoral head is known (see U.S. Pat. No. 8,145,319). Through the necrotic area of the femoral head an electric current is passed which stimulates the growth of bone tissue in the femoral head affected by arthrosis.
To carry out this method a device for electrostimulation of the bone tissue growth is used (see U.S. Pat. No. 8,145,319). The device includes a cathode and an anode remote from each other and connected with the battery by wires, and a control unit. The control unit and the battery are placed in an electrically conductive housing, which acts as the anode.
To begin the process of electrostimulation, you must first place the cathode in its permanent workplace. To do this it is necessary to perform a decompression dead hole in the femoral head affected by arthrosis. An axis of the hole is directed to an area of maximum lesion by necrosis. Then, the cathode is placed in this hole, using a dowel of a resorbable polymer. The cathode made of bare titanium wire is tightened by the dowel to the bottom of the decompression dead hole in order to ensure maximum electrical contact of the cathode with the necrotic area of a bone. The second function which is provided by the dowel is to hold the cathode in the hole in its place, ensuring conservation of the largest cathode contact with the walls and the bottom of the decompression hole. For this purpose, the dowel is placed into the decompression hole without a gap, i.e. closely. Later the dowel resolves and the cathode grows into the bone of the femoral head forever. An electricity wire comes out to the body surface from the bone. The electric current is supplied through the electricity wire to the battery.
After placement of the cathode by the pin in its place in the hole it is possible to begin to conduct electrical stimulation of the growth of healthy bone tissue. For this purpose the battery potential difference is supplied to the cathode and anode. Then, the anode is pressed against the patient's skin. A catenation closure occurs at that. The electric current starts to flow between the cathode and the anode through the body tissue of the patient, stimulating the growth of bone tissue of the femoral head. Because the decompression hole can be directed exactly to the area of maximum lesion by necrosis and it may be of any desired depth, the cathode can be placed in the optimal point of space of the femoral head, i.e. in the immediate vicinity of the zone of necrotic lesion that ensures the highest possible therapeutic effect on bone tissue.
A disadvantage of the method-analogue is that the electric current flowing from the cathode to the anode passes through tissues: skin, periosteum, fatty tissues and others. This leads to a loss of the battery energy and hence it requires recharging.
Also, the electricity wire coming out of the bone from the cathode passes through the skin of the patient outside and is a source of constant infection.
In addition, the therapeutic effect of the device requires a constant fixation of the housing-anode to the human body, creating a lot of discomfort in everyday life.
Furthermore, during the therapeutic effect process of the device the introduction of charged ions of the anode metal material leads to the poisoning of body tissues through which the current flows.
Another method for treatment of arthrosis is known. The method includes the periodic application (twice a day for 1 hour) of a paper plate on the skin surface of the joint affected by arthrosis. A dielectric coating in an electret state is formed on the surface of the paper plate (see http://www.uralargo.ru/article/489, http://precission.ru/?id_page=859373 and http://elis-deta.ru/elpast.html).
The disadvantage of this method for treatment of arthrosis is the distance of the electrostatic field generated by the electret coating from the joint lesion, which reduces the efficiency of this method-analogue, extending the treatment duration.
In addition, the periodicity of exposure to the lesion reduces the therapeutic effect duration of the electrostatic field of the electret coating, which also extends the treatment duration. Furthermore, when placing the plate on the surface of the movable joint, a mashing of a dielectric layer occurs, this leads to a loss of electret charge in it and makes the plate-analogue unsuitable.
These drawbacks are eliminated in the closest analogue.
Authors have chosen as the closest method-analogue a method for treatment of congenital hip joint malformation (see the USSR certificate of authorship No. 1,251,915), in which the femoral head occupies the wrong position relative to the pelvis, which leads eventually to the emergence of aseptic necrosis and degeneration of the head. During the treatment a portion of the femur is dissected (osteotomy), after that the femoral head is fixed in the correct position relative to the pelvis with the help of an electret implant.
The closest analogue is the electret implant according to the USSR certificate of authorship No. 1,251,915. The electret implant includes an extended body with a proximal and a distal end. The dielectric coating in an electret state is formed on its surface. Wherein the implant body is made as a plate. The proximal end is bent and is wedge-shaped, and two reach-through holes are made for screws at the distal end of the plate.
The closest method-analogue is implemented as follows: in the process of osteosynthesis the wedge-shaped end of the plate is hammered into the femoral head, and the distal end of the plate is tied to the second part of the femur, providing osteosynthesis. The electret potential along the plate distributes unevenly and has a maximum value in the osteotomy area (the bone dissection area) and in the wedge-shaped end of the plate.
Because the wedge-shaped end is placed into the pathological head, it is close to the bone pathology area. The electrostatic field generated by the electret coating having a maximum value at the wedge-shaped end, is as close as possible to the area of the necrotic lesion of the femoral head. This provides an increased electrostimulation of bone structures (compared to the previous analogue), leading to acceleration of the bone healing in the osteotomy area and prevention of development of destructive and degenerative processes in the femoral head.
Another disadvantage of the closest method-analogue is a violation of the electret coating integrity. Hammering of the wedge-shaped end into the femoral head is accompanied by friction of the electret coating on hard sharp chips. These chips are generated during hammering of the wedge-shaped end into the bone. During this process the violation of the electret coating integrity occurs in the wedge-shaped end zone, where a maximum electrostatic charge is concentrated. The violation of the electret coating integrity leads to a rapid discharge of the electret coating in the wedge-shaped end zone and weakening of the therapeutic action of the electrostatic field (until the complete action cessation) in the bone area where there is a maximum lesion of bone structures of the joint by the pathology.
The main purpose of the implant-analogue is osteosynthesis, i.e. a hard fixation of the femoral head relative to the dissected part of the femur during the treatment of the congenital disease associated with the wrong position of the head relative to the pelvis. The main thing that the electrostatic field of the electret coating works here on is osteosynthesis, i.e. stimulation of an accretion of parts of the dissected femur in the right mutual position relative to each other. The wedge-shaped proximal end serves here as a fastening element of a temporary design to the point when parts of the femur grow together and are able to perceive all loads of support-motor apparatus by yourself. Then the implant is removed from the bone because of its uselessness.
Thus, the main purpose of the electret coating on the implant surface is the optimization of osteosynthesis. The therapeutic effect of the electret coating electrostatic field on the surface of the wedge-shaped end gives an additional effect—an electrical stimulation of bone tissue inside the hip joint. It takes place during the accretion of dissected parts of the femur. After the implant removal the therapeutic effect of the electret coating electrostatic field on the joint pathology stops and pathological processes may be resumed.
Furthermore, the location of the electret implant toward the lesion of pathological destruction in the bone may not always be optimally chosen because the basic priority in choosing the direction of hammering of the wedge-shaped end of the implant into the bone is a high accuracy of the mutual position of connected parts of the bone (osteosynthesis). The optimization of osteoreparation is in second place, which reduces the efficiency of the therapeutic action of the electrostatic field on the pathological lesion in the bone.
Also, hammering of the wedge-shaped end increases the intraosseous pressure and requires drilling of several decompression holes in the bone (near the wedge-shaped end) to decrease the bone pressure. It further traumatizes the bone.
One more disadvantage of the electret implant which is the closest analogue is the magnitude of the total electrostatic charge on the wedge-shaped end of the implant. This is due to the fact that the proximal end of the implant is wedge-shaped, starting from a method of its application—hammering into the bone. On the edge of the wedge-shaped end, having a very small area, there is a proportionally small number of charges that proportionally reduces its impact on the effectiveness of reparative processes.
Another disadvantage of the implant-closest analogue is a dimensional limit for its placing in small-sized bones of arms and legs.
Also, implementation of the implant as the plate requires a large wrenching force to remove it from the hole in the case when the implant needs to be replaced.
Challenge arising from the prior art is a creation of a new treatment method, preventing the violation of an electret coating integrity during the implant placing into the bone.